Gravity die casting plant for metal-foam mouldings

ABSTRACT

A gravity die casting plant ( 1 ) for metal-foam mouldings comprises at least one die ( 2, 3, 4 ), one reservoir ( 16 ) for the metal melt and at least one metering and mixing device ( 11, 12, 13 ) for metering and mixing a foam-generating medium with the melt, at least one gate box ( 7 ) being arranged between the die ( 2, 3, 4 ) and the reservoir ( 16 ), and the metering and mixing device ( 11, 12, 13 ) being arranged in the gate box ( 7 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority from EuropeanApplication No. 05 022 025.0 filed Oct. 10, 2005.

BACKGROUND OF THE INVENTION

The invention relates to a gravity die casting plant for metal-foammouldings, comprising at least one die, one reservoir for the metal meltand at least one metering and mixing device for metering and mixing thefoam-generating medium with the melt.

In motor vehicle construction, in order to save weight, increasing useis made of castings and mouldings which are produced in part from metalfoam. The foam-generating medium used is a gas, for example air or inertgas, or a medium generating gas at the casting temperature. By means ofan impeller, as it is known, the gas or the gas-generating medium issupplied to the melt in a gate box and is distributed uniformly into themelt.

EP 1259344 B1 discloses a generic device for the production ofmetal-foam mouldings. A mould for the metal-foam mouldings has awidening inlet port which remains submerged in the melt during fillingwith the metal foam. An impeller agitator is arranged below the inletport in the melt. A gas supply is provided in the axis of rotation ofthe impeller agitator or directly adjacently to the agitator. Theintensity of intermixing and the foam content of the metal melt can beset.

Proceeding from this prior art, the object of the invention is tospecify a gravity die casting plant for metal-foam mouldings, in whichthe method parameters can be set as flexibly as possible.

SUMMARY OF THE INVENTION

The object is achieved by means of a gravity die casting plant formetal-foam mouldings, comprising at least one die, one reservoir for themetal melt and at least one metering and mixing device for metering andmixing the foam-generating medium with the melt, at least one gate boxbeing arranged between the die and the reservoir, and the metering andmixing device being arranged in the gate box.

It is advantageous that a plurality of metal-foam mouldings havingdifferent properties can be produced simultaneously in each castingcycle. This is achieved in that the gate box has a plurality of gateregions. This is also achieved in that a metering and mixing device formetering and mixing the foam-generating medium with the melt is arrangedin each gate region.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is described with reference tothe figures in which:

FIG. 1 shows a perspective view of a gravity die casting plant accordingto the invention, and

FIG. 2 shows a section through the gravity die casting plant of FIG. 1.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate diagrammatically a gravity die casting plant 1for the production of metal-foam mouldings, with three dies 2, 3, 4 nextto one another. FIG. 1 shows a perspective illustration and FIG. 2 alongitudinal section through the casting plant of FIG. 1. The dies 2, 3,4 are constructed in each case from two die halves 2 a, 2 b, 3 a, 3 b, 4a, 4 b. The dies 2, 3, 4 are installed between two insulating walls 5,6. Heating or coolant lines may be installed in the insulating walls 5,6. What is achieved thereby is that the dies 2, 3, 4 can be cooled orheated in a controlled way before and/or after the casting operation.What is achieved thereby is that the structure of the metal-foammoulding can be influenced by adherence to a temperature/time program.If the lines to each die 2, 3, 4 are activated separately, threemouldings with different structures and/or qualities can be produced inone casting operation. One moulding with three or more different regionsmay also be produced, however, if one large die is installed between theinsulating walls 5, 6, instead of three smaller dies.

A gate box 7 can be seen below the dies 2, 3, 4. The gate box 7 hasthree gate regions 8, 9, 10 arranged next to one another. Each die 2, 3,4 is thus assigned a gate region 8, 9, 10. If a large die is used, alarger metal-foam body with three differently formed regions can beproduced in one casting operation.

Three impeller agitators 11, 12, 13 are illustrated in FIG. 1perpendicularly to the plane of FIG. 2 and more clearly. The impelleragitators 11, 12, 13 are in each case assigned to a gate region 8, 9,10. The metal melt is agitated and gassed by means of the impelleragitator 11, 12, 13. For the formation of foam, a gaseous orfoam-forming medium, for example air or inert gas, is supplied to themelt in the die through ports in the impeller agitator 11, 12, 13. Theimpeller agitator 11, 12, 13 consists of a hollow rotatable shaft whichprojects into the respective gate region 8, 9, 10 from the side into themetal melt and which drives at the shaft end a vane wheel or an impellerhaving gas outlet ports. By means of the impeller agitator 11, 12, 13,in each gate region 8, 9, 10, air or inert gas or anotherfoam-generating medium is supplied or metered in a defined quantityratio to the melt and mixed with the metal melt. By the impelleragitator 11, 12, 13 being arranged directly below the die 2, 3, 4, theformation of foam takes place in the die 2, 3, 4 already filled withmelt. As a result of the excess pressure which is generated by theimpeller by means of the gas supply, part of the melt is driven out ofthe die 2, 3, 4 back into the gate box 7.

Foam formation and the stabilization of the foam can be improved if themelt has added to it solid particles which have a beneficial influenceon the surface tension at the interface between the gas and the metalmelt. Instead of the impeller agitator 11, 12, 13, another suitablemetering and mixing device may also be installed. It is also conceivablethat a plurality of gate regions 8, 9, 10 are operated by means of oneimpeller agitator 11, 12, 13, so that two cast mouldings having the sameproperties can be produced simultaneously.

The gate box 7 has on the underside a connection 14 for a riser pipe 15or another line for connecting the metal melt to a reservoir 16. In thealready known rising low-pressure casting method, as it is referred to,the riser pipe 15 is immersed in the reservoir 16, and the reservoir 16is closed off and acted upon by pressure, for example by inert gas.Owing to the pressure on the melt surface in the reservoir 16, the metalmelt rises into the riser pipe 15 and into the gate box 7. It is alsoconceivable to fill via a plurality of riser pipes 15 a plurality ofgate boxes 7 which could then, in turn, fill one or more dies 2, 3, 4.The metal melt may be a light-metal melt, for example an aluminium ormagnesium melt. The gravity die casting plant 1 may, however, also bedesigned for other metals. The solid particles which may be added forfoam formation are administered in the reservoir 16 or in the meltingfurnace for the melt.

By means of the gravity die casting plant 1 described here, the methodparameters for each gate region 8, 9, 10 and for each die 2, 3, 4 can beset separately. The chemical parameters of the melt can be varied byadditions in the gate box 7. The temperature of the melt or of the metalfoam can be varied by the preheating or precooling of the die 2, 3, 4 orby additional heating which may be installed in each gate region 8, 9,10 of the gate box 7. By the action of pressure upon the reservoir 16,the casting speed can be set. Foam formation and foam consistency can beset by means of the gas quantity and the impeller speed. A separatetemperature/time curve can be achieved for each die 2, 3, 4 by means ofa control of the holding times.

Metal-foam bodies with different geometries can be producedsimultaneously or, if one large die is connected to a plurality of gateregions 8, 9, 10, a larger metal-foam body with differently foamedregions can be produced. Larger castings may also be produced, which arefoamed in some regions, but in other regions are not foamed, that is tosay are filled completely.

1. Gravity die casting plant (1) for metal-foam mouldings, comprising at least one die (2, 3, 4), a reservoir (16) for the metal melt and at least one metering and mixing device (11, 12, 13) between the reservoir and the at least one die for metering and mixing a foam-generating medium with the melt, wherein at least one gate box (7) is arranged between the die (2, 3, 4) and the reservoir (16), and the metering and mixing device (11, 12, 13) is arranged in the gate box (7).
 2. Gravity die casting plant (1) for metal-foam mouldings according to claim 1, wherein the gate box (7) comprises a plurality of gate regions (8, 9, 10).
 3. Gravity die casting plant (1) for metal-foam mouldings according to claim 1, wherein the metering and mixing device (11, 12, 13) for metering and mixing the foam-generating medium with the melt is arranged in each of a plurality of gate regions (8, 9, 10) of the gate box (7).
 4. Gravity die casting plant (1) for metal-foam mouldings according to claim 3, wherein each of a plurality of dies (2, 3, 4) is arranged so as to be connectable to a gate region (8, 9, 10).
 5. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein at least one gate region (8, 9, 10) is arranged so as to be connectable to each die (2, 3, 4).
 6. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein each die (2, 3, 4) has a different geometry.
 7. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein the gate regions (8, 9, 10) in the gate box (7) are arranged so as to be spatially separated from one another.
 8. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein the dies (2, 3, 4) and/or the gate box (7) are/is designed with a heating and/or cooling system.
 9. Method for the production of metal-foam mouldings in a gravity die casting plant according to claim 1, comprising the steps of: feed of the melt in the reservoir (16), build-up of pressure in the gravity die casting plant (1), the melt being pressed from the reservoir into the gate box (7) and into the die (2, 3, 4), introduction of gas into the melt, discharge of pressure from the gravity die casting plant (1), and adherence to a holding time for cooling the die (2, 3, 4), wherein the gas is introduced by means of an impeller agitator (11, 12, 13) in the die (2, 3, 4) filled with melt, and in that, during the casting operation, at least the method parameters comprising the density of the metal foam and the temperature in the gate box (7), in the gate region (8, 9, 10) and in the die (2, 3, 4) can be set and controlled independently of one another in each gate box (7), in each die (2, 3, 4) and in each gate region (8, 9, 10). 